As a 3DCG application, virtual malls on internet, e.g., WWW (world wide web) and various homepages have been noticeable. Particularly, the rapid developments of internet helps to improve the circumstances in which 3DCG of such as games and movies are readily handled at home.
In a conventional WWW, a machine called "server," such as a personal computer (PC) and workstation, is connected, through internet, to a plurality of machines called "client," such as PC. In response to the demand of a client, as required, data including information on picture image, voice, text and layout provided by a server is downloaded, and then reconstructed at the client side to obtain necessary information. In such communication between servers and clients, there is utilized a communication procedure based on TCP/IP (transmission control protocol/internet protocol).
Conventional data provided by servers were mainly text data and picture image data. Recently, the standardization of VRML (virtual reality modeling language) and the browser of the VRML advanced, and the modern trend is toward the transfer of 3DCG data itself, such as shapes and scenes.
Brief description will be given of the VRML. To transfer picture data, particularly moving picture data using a conventional data format mainly for picture image and text, e.g., HMTL (hyper text markup language), requires much transfer time and costs. Therefore, network traffic restriction is imposed on the present-day system. In a conventional 3DCG, shape, viewpoint and lighting information were all processed by three-dimensional data. As computer graphics (CG) technology is advanced, the image quality of picture image created by CG is rapidly improved. In view of data quantity, it is more efficient to transfer CG data as it is. In this case, data compression ratio is normally not less than 1/100 of the transfer of the equivalent picture image data. Therefore, the modern trend is toward the standardization of the transfer method of 3DCG data through network. As an attempt, the standardization of 3DCG data called "VRML" has been proposed (VRML Ver. 2.0). The VRML Ver. 2.0 defines, for example, shape data called "primitive," data format of various lighting source data, viewpoint data and texture data, and the designation process of rigid body motion.
Among the conventional CG field, animation that produces picture image in real-time, i.e., so-called real animation, is worthy of remark. The reproduction of the real motion of CG characters utilizing a real animation, is being studied mainly in the field of CM (commercial message) and movies. There are for example a method called "kinematics method" in which a complex shape such as human being is represented by a skeleton structure (hierarchical structure), and its complex motion is reproduced naturally by the definitions of the motion quantity of the joints of skeletons that change from time to time.
The aforementioned kinematics method was primarily developed in the-field of robotics engineering. This method is to decide the posture of a skeleton model having a linear link structure comprising links and joints, by setting the angle of rotations in the directions of X, Y and Z axes of the joint parts of the skeleton model, and the motion quantity (position) in the directions of X, Y and Z axes.
By utilizing the kinematics method in a character of an arbitrary skeleton structure created by CG, it is being able to decrease the data quantity and reproduce natural motions of such as human being and dinosaurs, compared to a conventional polygon based animation that is created by the simultaneous use of key frame method and the like.
In 3DCG modeling language on a conventional internet in which VRML plays a central role, however, it is present condition that no consideration is given to methods for defining continuous time series motions of objects, and that there is no method for defining the motions of complex shapes of human being and the like, i.e., natural postures of hands and feet.
In a conventional animation creation based on kinematics method, the creation of smooth motions requires much motion data. In terms of applications to network, traffic issue is left unsettled.